40 lines
1.1 KiB
Rust
40 lines
1.1 KiB
Rust
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// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// A test for something that NLL enables. It sometimes happens that
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// the `while let` pattern makes some borrows from a variable (in this
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// case, `x`) that you need in order to compute the next value for
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// `x`. The lexical checker makes this very painful. The NLL checker
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// does not.
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#![feature(nll)]
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use std::rc::Rc;
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#[derive(Debug, PartialEq, Eq)]
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enum Foo {
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Base(usize),
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Next(Rc<Foo>),
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}
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fn find_base(mut x: Rc<Foo>) -> Rc<Foo> {
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while let Foo::Next(n) = &*x {
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x = n.clone();
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}
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x
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}
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fn main() {
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let chain = Rc::new(Foo::Next(Rc::new(Foo::Base(44))));
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let base = find_base(chain);
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assert_eq!(&*base, &Foo::Base(44));
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}
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